1. Field of the Invention
The present invention relates to printers and more particularly to improved printers that use micro electro-mechanical switches to decrease cost and improve performance.
2. Description of the Background Art
Two common types of printers in wide use are the laser printer and the ink jet printer that are designed for both home and office. The laser printer is a well-known and commercially successful type of indelible printer. It utilizes static electricity to build up an electrical charge on a photoreceptor made out of highly photoconductive material. This material looses a charge when activated by light photons from the laser. Since the laser draws the image of the page onto the photoreceptor, a scanning assembly is needed to scan the laser across the photoreceptor and this assembly must be incredibly precise.
The typical laser scanning assembly includes a laser, a movable mirror and lens, all of which are expensive. The laser is modulated to print tiny dots that make up the image to be printed one horizontal line at a time. As the laser beam moves across the photoreceptor, the laser emits a pulse of light for every dot to be printed, and no pulse where a dot is not to be printed. Because the laser doesn't actually move the beam itself, the laser beam is bounced off of the moveable mirror. As the mirror moves, it shines the laser beam through a series of lenses that compensate for image distortion caused by the varying distance between the mirror and dots along the photoreceptor. In a laser printer, the mirror spins incredibly quickly and is synchronized with the laser switching on and off. A typical laser printer will switch millions of times every second.
The charged photoreceptor attracts electrically charged toner in the shape of the image that is then transferred onto a sheet of paper. The sheet of paper is then heated to fuse the toner to the paper. The laser printer is typically preferred for business applications because the printed image is indelible which means that it will not smear, smudge and is generally of archival quality.
A major disadvantage of the laser printer is the cost of the components and specifically the cost of the laser, the laser scanning system and the photoreceptor. Not only are these components expensive, they are also subject to wearing out and the photosensitive drum requires regular replacement. Further, the process of getting the image from the computer to the paper requires sophisticated control software and electronics, optics, mechanics and chemistry. Because of high cost components and system complexity, laser printers are relatively expensive so what is needed is a simple, indelible printer that does not require expensive components such as the laser, scanning optic or a photoreceptor.
Another type of commonly used printer is the ink jet printer. Ink jet printers are relatively inexpensive compared to laser printers because they use charged particles or ink rather than toner. Ink jet printers work on the principle that a printing head by means of several physical principles, e.g., heat, ultrasonic pulse, etc., is made to eject a small ink droplet onto an absorbent paper. The droplets form the desired graphical image. Ink jet printers produce different colors by mixing at least cyan, magenta, and yellow inks and can accurately create an extremely large range of colors. Ink jet printers are often used to print digital photographs. The major disadvantage of the ink jet printer is that the printed image tends to fade rather quickly, often in as little as three to six months. The image is not moisture-fast, and images with significant quantities of deposited ink are often wrinkled by the moisture. It is clearly desirable to provide a low cost indelible color printer.
With respect to ink jet printers, conservation of ink is clearly desirable. For this reason many ink jet printers utilize drop on demand technology where a ink drop is generated only when needed. Many other ink jet printers generate a continuous stream of ink that relies on the deflection of drops that are to be applied to the paper. The non-deflected drops are collected and recycled. However, recycling ink drops can introduce air to the ink reservoir and is generally undesirable. The drop on demand technology utilizes piezo-electrical crystals that change their dimensions when an electrical current is applied to generate a drop. Such crystals are expensive so a lower cost alternative to generate a drop of ink is necessary.
Another disadvantage of current printers is that lack of a low cost printer that can print on paper that is wider than about twelve inches. It would be advantageous if a printer could print on paper having a width that exceeds twelve inches.